番茄低氮敏感突变体基因的克隆与功能分析

Nitrogen is a largest mineral nutrient in plant,and is also a nutrient mostly limiting crop growth and development in agricultural production.It becomes a serious environmental problem due to over-application of nitrogen fertilizer in agriculture. Therefore, studying the molecular mechanisms of nitrogen uptake and assimilation in plant is very important for protecting enviroment and sustaining development of agriculture. In this application, we use a low-nigtrogen sensitive mutant lnsm1 of tomato as research plant material, and isolate its corresponding gene using map-based gene cloning approach. Futher, the expression patterns of the genes related to nitrogen uptake and assimilation and the physilogical parameters related to nitrogen uptake and assimilation will be determined with physiological and molecular approaches, and they will be comparatively analyzed between lnsm1 mutant and its wild type under the conditons with different nitrogen supply. Finally, the changes of subcellular structures of leaf mesophyll cells of the mutant and wuld type will be investigated under eletronmicrospoces under different nitrigen supply. Taken all together, the bilogical functions of LNSM1 will be illustrated. The results will be useful for understanding the molecular mechanisms of nitrogen uptkae and assimilation in plants and for improvement of nitrogen use efficiency in crops.

氮是植物体内含量最大的矿质营养元素，也是农业生产中限制作物生长发育的主要缺素.氮肥的大量施用导致了严重的坏境污染,因此研究植物氮吸收同化的分子机制，培育氮高效作物新品种对保护环境和保证农业的可持续发展具有重要意义。 本申请以一个番茄低氮敏感突变体lnsm1为材料，用图位克隆法分离其相关基因，并用生理和分子生物学方法系统地比较分析突变体与野生型在不同氮素供应条件下各种与氮吸收同化的生理指标和相关基因表达的变化，结合突变体和野生型叶组织细胞学观察结果，揭示LNSM1基因的生物学功能，为培育氮高效新品种提供理论依据和基因资源。

氮素是植物体内蛋白质、核酸、磷脂和一些生长激素的重要组分。在农业生产中，氮素的缺乏是限制作物产量提高的重要因素。因此，研究植物氮代谢的分子机制和分离调控植物氮素利用效率的关键基因，可以从生物学途径为改良作物氮素的吸收和利用提供科学依据和基因资源。.番茄（Solanum lycopersicum）是一种重要的蔬菜作物，也是研究植物生理代谢的模式植物。本研究的番茄lnsm1是自然发生的、叶黄化和果实白化的突变体。在营养生长时期，lnsm1的叶片自下而上出现黄化。本研究发现该突变体是一个低氮敏感突变体，施加高浓度的硝酸盐或铵盐能使黄化叶片恢复绿色。通过图位克隆，分离到了控制该性状的基因SlEGY1。SlEGY1基因在根、茎、叶、花和果实中都有表达，且在叶中的表达量高于其它组织，但该基因的表达不响应环境中氮浓度的变化。SlEGY1基因的编码蛋白主要定位在叶绿体膜上。氮含量分析结果表明SlEGY1调控了氮的吸收或利用。定量PCR和转录组测序的结果表明，SlEGY1不仅调控了低氮条件下与氮吸收和转运有关基因如NRT1.1、NRT1.2 NRT1.5和AMT2.1 的表达，还调控了低氮条件下与乙烯合成和信号转导相关基因的表达。乙烯测定结果也表明EGY1的缺失影响了低氮条件下乙烯的合成。以上结果表明EGY1的生物学功能是通过调控乙烯的合成影响了缺氮条件下氮的吸收和转运。